title: Secondhand smoke and adverse fetal outcomes in nonsmoking pregnant women: a meta-analysis.
abstract: OBJECTIVE
  To determine the risk of adverse fetal outcomes of secondhand smoke exposure in nonsmoking pregnant women.
  
  
  METHODS
  This was a systematic review and meta-analysis in accordance with Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. We searched Medline and Embase (to March 2009) and reference lists for eligible studies; no language restrictions were imposed. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were estimated by using random-effect models. Our search was for epidemiologic studies of maternal exposure to secondhand smoke during pregnancy in nonsmoking pregnant women. The main outcome measures were spontaneous abortion, perinatal and neonatal death, stillbirth, and congenital malformations.
  
  
  RESULTS
  We identified 19 studies that assessed the effects of secondhand smoke exposure in nonsmoking pregnant women. We found no evidence of a statistically significant effect of secondhand smoke exposure on the risk of spontaneous abortion (OR: 1.17 [95% CI: 0.88-1.54]; 6 studies). However, secondhand smoke exposure significantly increased the risk of stillbirth (OR: 1.23 [95% CI: 1.09-1.38]; 4 studies) and congenital malformation (OR: 1.13 [95% CI: 1.01-1.26]; 7 studies), although none of the associations with specific congenital abnormalities were individually significant. Secondhand smoke exposure had no significant effect on perinatal or neonatal death.
  
  
  CONCLUSIONS
  Pregnant women who are exposed to secondhand smoke are estimated to be 23% more likely to experience stillbirth and 13% more likely give birth to a child with a congenital malformation. Because the timing and mechanism of this effect is not clear, it is important to prevent secondhand smoke exposure in women before and during pregnancy.
authors.affiliation: UK Centre for Tobacco Control Studies, Division of Epidemiology and Public Health, University of Nottingham, Nottingham, United Kingdom. jo.leonardi-bee@nottingham.ac.uk
authors.forename: Jo
authors.initials: J
authors.lastname: Leonardi-Bee
authors.forename: John
authors.initials: J
authors.lastname: Britton
authors.forename: Andrea
authors.initials: A
authors.lastname: Venn
mesh_terms: D000022:Abortion, Spontaneous / Q000209:etiology*; D000013:Congenital Abnormalities / Q000209:etiology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000401:mortality*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D018570:Risk Assessment; D050497:Stillbirth; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D014028:Tobacco Smoke Pollution